The electrophotographic method that forms an electrostatic image (electrostatic latent image) on a photoconductor drum, visualizes the image by toner, and transfers the image to a sheet (or paper-like medium such as paper) is generally deemed to be mainstream for an image forming apparatus such as a copying machine and printer used in an office or the like. The inkjet method that forms an image by directly spraying ink droplets onto a sheet is mostly adopted for a relatively small printer such as a home-use printer. An image forming apparatus called a copying machine or printer to form an image includes a sheet conveying apparatus to convey a sheet to an image forming unit or to deliver a sheet on which an image is formed.
In an image forming apparatus including a sheet conveying apparatus, a sheet (or paper-like medium such as paper) is picked up from a sheet feeding cassette or manual sheet feeding tray and conveyed by the sheet conveying apparatus, and the inclination of the sheet is adjusted by a registration roller before the sheet is fed to an image forming position where an image is transferred to the sheet. When a sheet is fed to the image forming position, element sounds such as an operation sound of a pickup roller and conveying rollers, an operation sound caused when these rollers start to be driven from a stopped state, and a collision sound (impulsive sound) when a sheet collides against the registration roller are caused. Such element sounds are caused also by other components attendant on conveying a sheet and perceived as noise. Moreover, element sounds are repeated as many times as the number of sheets to be printed. An image forming apparatus is mostly installed in an office environment or the like and an influence of noise spreads not only to the user of the apparatus, but also to workers therearound. If irregular impulsive sounds are caused frequently, it is annoying for the user of the apparatus and workers therearound and operating efficiency could adversely be affected.
In a conventional sheet conveying apparatus, various ideas to reduce such noise are implemented. For example, JP-A 2003-118888 (KOKAI) and JP-A 2006-248650 (KOKAI) disclose sheet conveying apparatuses that reduce an impulsive sound caused when a sheet is carried out of a sheet feeding cassette. However, even if measures against noise are taken, reducing the noise level to an audible level or below is deemed to be realistically impossible. Thus, it is difficult to eliminate annoyance to the user of the apparatus and workers therearound.
“Designing for Product Sound Quality”, Richard H Lyon, p. 1-10, June 2000, on the other hand, proposes product sound quality (PSQ) that considers a working sound arising from a product not as noise, but as a sound and enhances product value by designing a product sound. Instead of minimizing the noise level by considering a working sound of a product simply as noise, this idea designs sound as a portion of the product.
While conventional sheet conveying apparatuses disclosed by JP-A 2003-118888 (KOKAI) and JP-A 2006-248650 (KOKAI) can reduce the generated noise to some extent, there is a problem that noise cannot be completely got rid of, thus a sheet conveying apparatus capable of reducing annoyance caused by noise is demanded.